Conventional pedaling devices (e.g. bicycles, stationary bicycles) have a crank that includes a shaft that provides a mechanical connection between right and the left arms. In operating the crank, force applied to one arm moves the other arm via force transmitted through the shaft.
People who have suffered from a stroke can exhibit at least two problems when using their lower limbs. Patients may underutilize the paretic limb. Patients may also have difficulty properly coordinating the output of the paretic and non-paretic limbs. When stroke patients pedal a conventional pedaling device with a mechanical connection between the two arms, often the non-paretic limb will be relied upon to turn the crank to move the paretic limb. This strategy is advantageous to stroke patients because it allows them to complete the pedaling task. However, by completing the task in this manner, stroke patients fail to improve the motor output of the paretic limb and do not learn to coordinate the output of the paretic and non-paretic limbs. Consequently, motor recovery may be impeded.
Reliance upon the non-paretic limb can be addressed by “uncoupling” or “splitting” the crank at the shaft. When the crank shaft is split, the mechanical connection between the paretic and non-paretic limbs is eliminated. Thus, to pedal successfully, the paretic limb must generate force, and movement of each limb must be properly coordinated. In this manner, both challenges for stroke patients should be rehabilitated and improved with practice.
However, this solution is not available in clinical practice as split crank pedaling can be challenging to even people without stroke and can be too difficult to accomplish for some stroke patients. Due to the difficulty of even completing the motions with both paretic and non-paretic limbs, patients can become frustrated and quit treatment due to their inability to perform the requested tasks. Even when patients may continue with the treatment, the patients may repeatedly fail the task or exhibit such poor form or improper movement that the patients do not receive the desired movement practice or rehabilitation. Thus, the physical tasks presented by a split-crank pedaling device are beyond the physical capabilities of many stroke patients and thus rehabilitation efforts using such currently known devices are not effective as the patients either become frustrated and discouraged or practice improper movements, limiting rehabilitative effect.
Currently available split-crank bicycles can provide motor-controlled assistance and resistance torque to the cranks of the pedals. One example is described in Van der Loos, H. F. Machiel, “A Split-Crank, Servomotor-Controlled Bicycle Ergometer Design for Studies in Human Biomechnics.” IEEE/RSJ Int. Conference on Intelligent Robots and Systems EPFL (October 2002), which is hereby incorporated by reference in its entirety. However, such split-crank bicycle is adapted as an ergometer for biomechanic investigation. The systems, operations, and controls are not adapted for treatment of patients through physical therapy, training, or rehabilitation. Therefore different solutions for these purposes are needed.
U.S. Pat. No. 6,234,939 discloses a unipedal cycle apparatus in which each of the right and left sides of a cycle have independent drive systems. The resistance on each drive system can be controlled independently by a microprocessor to increase or decrease the tension on a brake belt for the left and right drive systems. However, this is only related to variable resistance and does not provide assistive support.
U.S. Pat. No. 7,727,125 discloses an exercise machine and method for use in training selected muscle groups with resistance to split crank rotations. An inertia of the bike/rider system is simulated as would be experienced when riding a conventional bicycle by executing a stored training program with predetermined changes to crank resistance based upon crank position.
U.S. Pat. No. 8,602,943 discloses an exercise apparatus and a brake mechanism where a reciprocating activation means in response to a measured force exerted on the reciprocating activation means. The controller operates the system to provide assistance or resistance to a pedal stroke or a portion of a pedal stroke to maintain the system operation within a predefined cycle range.